<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>title</title>
    <script src="https://cdn.bootcdn.net/ajax/libs/vue/2.6.13/vue.min.js"></script>
</head>

<body>

    <div id="app">

        <span>{{ msg }}</span>

    </div>
    
</body>
<script>

 const mv = new Vue({
     el:'#app',
     data:{
         msg:'这是个消息'
     }
 })

</script>

</html>